Cory,
If you are already at 640 x 480, you will need a photo app to resize it. Some photo apps, like the one in the example I used in the thread Andrew linked for you, use the term, "optimize". You can reduce, or optimize the "quality" by percentages until you get the file down to 65K or less. Reducing the pixel size is easy too, but again, you need a photo app if you're going to do both.
If you don't have a photo app, let me know and I can tell you were to get one that will do the job at no cost. Free is good.